Nanohardness and structure of nitrogen implanted SixAly coatings post-implanted with oxygen

"Sialons" have several interesting mechanical, thermal and chemical propert ies which make them candidates for high temperature applications. Solid sol utions in the Si-Al-O-N system were synthesised using nitrogen and oxygen i mplantation into Si33Al67, Si45Al55 and Si67Al33 thin films deposited by DC magnetron sputtering on glassy carbon substrates. Nitrogen has been implan ted firstly at 50 and then at 20 keV, oxygen was post-implanted at 50 keV. The different implantation doses ranged from 1 to 10x10(17) ions/cm(2), Hig h depth resolution profiles were obtained using RES and resonant nuclear re action, the chemical bonds were investigated using LEEIXS and these results are correlated to the film structure measured by cross section TEM, The TE M micrographs show a columnar structure perpendicular to the substrate surf ace in unimplanted coatings. Nevertheless, when nitrogen is implanted grain formation is observed and after oxygen post-implantation gas bubbles appea r at the film depth where the maximum oxygen concentration is observed. The correlation of these results with RES and LEEIXS measurements indicates th at nitrogen should be enclosed in these bubbles. Nanohardness was also meas ured. The highest values are observed in samples post-implanted with 1x10(1 7) O/cm(2) where nanohardness increases from 3 to 10 Gpa. (C) 1999 Publishe d by Elsevier Science B.V. All rights reserved.